Currently, 3GPP (3rd Generation Partnership Project) proposes a brand-new EPS (evolved packet system) network including UE (user equipment), an eNB (Evolutional Node B, E-UTRAN Node B), an SGW (Serving Gateway), a PGW (packet data network gateway), and an MME (mobility management entity). The SGW serves as a forwarding plane anchor between access networks, and the PGW serves as a forwarding plane anchor between an access network and a non-access network. To ensure continuity of IP addresses of the UE, the PGW is deployed at a relatively high position. In this way, even if the UE moves, the UE always keeps connection to the PGW, thereby ensuring that an IP address remains unchanged. However, if the UE accesses a local server, a route recurvation problem occurs, that is, data of the UE first arrives at the PGW at a relatively high position, and then returns to the local server. Consequently, a packet transmission delay gets longer.
To resolve this problem, 3GPP defines an SIPTO (Selected IP Traffic Offload) function. A core idea of the SIPTO function is to deploy the SGW and the PGW at low positions. When the UE accesses the local server, a local PGW allocates an IP address, and data passes through only a local SGW and the local PGW, thereby avoiding route recurvation, and resolving a problem of an extremely long packet transmission delay. However, a disadvantage of deploying the SGW and the PGW at low positions is that the SGW and the PGW are relatively far away from a centrally deployed MME, and consequently a signaling transmission delay gets longer when the UE switches from an idle state to an active state. Therefore, another method for reducing the signaling transmission delay is to shift the MME downwards to a low position and deploy the MME and the local gateway together. However, this greatly reduces a quantity of UEs managed by each MME. When UE moves, the UE tends to switch between different MMEs, and consequently signaling interaction increases, and system load increases.